Biology Study Set 13

Biology

Quiz 49 :
Human Impacts on the Biosphere

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Quiz 49 :
Human Impacts on the Biosphere

Sexual imprinting is defined as the mechanism by which a young bird learns characteristics of its specific species that helps it to find a conspecific mate when it reaches adulthood. The birds acquire this knowledge from the parents. The figure suggests that the rooster was exposed to ducks during its imprinting period, and hence after the rooster matured, it preferred to mate with ducks rather than with birds of its own kind.

Genes in any species play a direct role in the development of nervous systems. The products of genes are necessary to construct and operate the sensory receptors, nerves and in complex higher animals, the brain. The gene products thereby play a role in the behavioral responses of the organisms to stimuli. Several hormones (signaling molecules secreted by the endocrine lands ) are also products of some genes. Therefore the answer is d. all of the above

The Nazca boobies lay two eggs but the elder hatchling kills the younger one and only one survives to adulthood. And this is independent of the availability of food. Two eggs are laid instead of one, in order to ensure that even if one egg gets lost by being eaten by predator, or by physical damage, one will survive. However, the fact that only one survives and the other is deliberately killed can be attributed to the fact that the Nazca boobies have to travel sixty miles for fishing and the entire travel consumes two hours, hence the bird can make at the most two trips during the daylight period fetching food for one chick. The other parent has to stay in the nest taking care of the chick. Hence gathering enough food for two chicks is energy expensive. Hence these species have been naturally selected to practice obligate siblicide. The hypothesis can be tested by growing the chicks separately giving both chicks equal amount of food and then checking their survival.

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